Study: Effects of soot vary with altitude

PALO ALTO, Calif., April 14 (UPI) -- The effect of black carbon -- soot -- on climate change depends on the altitude at which it is found in the atmosphere, U.S. researchers say.

Black carbon -- emitted from diesel engines, burning wood and other sources -- acts as an absorbing aerosol, a particle that absorbs the sun's heating rays, researchers at the Carnegie Institution in California said.

The researchers ran simulations of adding a theoretical 1 million tons of black carbon uniformly around the globe at different altitudes in the atmosphere, a Carnegie release said Thursday. They found the addition of black carbon near the land and ocean surface caused the surface to heat, but surface warming decreased as the altitude of the soot increased.

The simulated addition of black carbon to the stratosphere caused the opposite effect, cooling the land and oceans even though the soot caused Earth as a whole to absorb more energy from the sun.

This is because when black carbon is high in the atmosphere it can lose its energy to space while helping to shade the land and ocean surface, the researchers said.

"Unfortunately, this is exactly where we are putting most of the black carbon that we add to the atmosphere. This black carbon also often causes health problems, so cleaning up these emissions would help both the environment and human health."

United Press International is a leading provider of news, photos and information to millions of readers around the globe via UPI.com and its licensing services.

With a history of reliable reporting dating back to 1907, today’s UPI is a credible source for the most important stories of the day, continually updated - a one-stop site for U.S. and world news, as well as entertainment, trends, science, health and stunning photography. UPI also provides insightful reports on key topics of geopolitical importance, including energy and security.

A Spanish version of the site reaches millions of readers in Latin America and beyond.

UPI was founded in 1907 by E.W. Scripps as the United Press (UP). It became known as UPI when after a merger with the International News Service in 1958, which was founded in 1909 by William Randolph Hearst. Today, UPI is owned by News World Communications.